Gasification apparatus and method

ABSTRACT

A gasification system is disclosed having a combustion or reaction vessel, a scrubber housing, and a filter housing. A carbonaceous fuel is partially combusted in the reaction vessel to generate a combustible gas. An improved ash support and removal system reduces clogging and other problems in the reaction vessel. The combustible gas passes through the scrubber housing to remove matter such as tar and oil, and the scrubbed gas passes through a hybrid blower to the filter housing. Wood chips are used in the filter housing to provide a relatively clean, dry gas. Wastewater and other waste products from the scrubber housing and filter housing are captured and returned to the reaction vessel.

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/492,363, filed on Aug. 4, 2003.

BACKGROUND OF THE INVENTION

This invention relates to gasification and, more particularly, to aflexible gasification apparatus and method that provides combustiblegases having high heating values while avoiding pitfalls of priorattempts at gasification.

Gasification has generally been known for years. In gasification, acarbonaceous fuel source is partially combusted to produce a combustiblegas, synthesis gas, or syngas. The combustible gas is then combusted toproduce work. The combustible gases produced by gasification may findany number of uses, including but not limited to supplying heat,powering a motor, or producing electricity. Gasification provides manyadvantages, such as allowing fuels having relatively low heating valuesto be used, allowing waste products to be used to produce work, and,similarly, reducing the amount of waste material that must be sent tolandfills. Despite these obvious advantages, gasification has met withonly limited success, because gasification systems have typically beenplagued by a number of disadvantages or difficulties. For example, theheating values of gases produced using prior art systems have tended tofluctuate to an undesirable degree, particularly when a variety of fuelsources or fuel sources of varying compositions have been used.Similarly, it has also proven difficult to consistently produce gaseshaving sufficiently high heating values. Separating particulate matterfrom the produced gas has proven problematic. Similarly, it has provendifficult to produce sufficiently clean gases having sufficiently lowamounts of particulate matter as well as sufficiently low amounts ofpollutants such as such as sulfur dioxide (SO₂), nitrogen oxides(NO_(x)), carbon monoxide (CO) and volatile organic compounds (VOC),ammonia, hydrogen chloride (HCl), and chlorides. Environmentally sounddisposal of wastewater generated by such systems has also presenteddifficulties. Further still, the presence of water or other liquids inthe combustible gas has made it difficult or impossible to use blowersfor moving the combustible gases without creating undesirable levels ofwear and tear on the blowers.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a flexiblegasification apparatus and method that provides combustible gases havinghigh heating values while avoiding pitfalls of prior attempts atgasification.

It is a further object of the present invention to provide an apparatusand method of the above type that can easily handle a wide variety ofcarbonaceous fuel sources or combinations of fuel sources.

It is a further object of the present invention to provide an apparatusand method of the above type that produces a high value heating gashaving low amounts of particulate matter and other pollutants.

It is a further object of the present invention to provide an apparatusand method of the above type that requires little or no wastewaterdisposal.

It is a still further object of the present invention to provide anapparatus and method of the above type that captures a relatively highfraction of the potential heating value of the fuel sources.

It is a still further object of the present invention to provide anapparatus and method of the above type that safely and cleanly consumesa wide variety of agricultural and industrial byproducts, including butnot limited to animal waste and wood pulp sludge.

It is a still further object of the present invention to provide anapparatus and method of the above type that is less prone to cloggingproblems typically associated with ash removal.

It is a still further object of the present invention to provide anapparatus and method of the above type that may easily process a widevariety of combinations of solid and liquid fuels.

It is a still further object of the present invention to provide anapparatus and method of the above type that can safely and efficientlyhandle and dry relatively wet combustible gases.

It is a still further object of the present invention to provide anapparatus and method of the above type that uses a rugged, hybrid blowerthat can safely and efficiently handle both dry and relatively wetcombustible gases.

Toward the fulfillment of these and other objects and advantages, thesystem of the present invention comprises a combustion or reactionvessel, a scrubber housing, and a filter housing. A carbonaceous fuel ispartially combusted in the reaction vessel to generate a combustiblegas. An improved ash support and removal system reduces clogging andother problems in the reaction vessel. The combustible gas passesthrough the scrubber housing to remove matter such as tar and oil, andthe scrubbed gas passes through a hybrid blower to the filter housing.Wood chips are used in the filter housing to provide a relatively clean,dry gas. Wastewater and other waste products from the scrubber housingand filter housing are captured and returned to the reaction vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

The above brief description, as well as further objects, features andadvantages of the present invention will be more fully appreciated byreference to the following detailed description of the presentlypreferred but nonetheless illustrative embodiments in accordance withthe present invention when taken in conjunction with the accompanyingdrawings, wherein:

FIG. 1 is a flow diagram of a system for practicing the presentinvention;

FIG. 2 is a side elevation, schematic view of a combustion or reactionvessel for practicing the present invention;

FIG. 3 is an overhead, schematic view of a blower for practicing thepresent invention; and

FIG. 4 is a side elevation view of an impeller for practicing thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, the reference numeral 10 refers in general to agasification system for practicing the present invention. The system 10will typically comprise a combustion or reaction vessel 12, a scrubberhousing 14, and a filter housing 16, and may also include a recyclehousing 18.

Referring to FIG. 2, the reaction vessel 12 has an upper, outer wallportion 20 and a lower base portion 22. The reaction vessel 12 is openat the top. A feed line or conduit 24 is disposed above the vessel 12 toprovide a carbonaceous fuel source. Another feed line 26 may also beprovided to return waste material from other portions of the system 10as discussed in more detail below. Additional feed lines may also beused, for example, to provide different types of solid and liquid fuelsources. An inner wall 28 is disposed within the vessel 12 and isconnected to the vessel 12 to form an inner chamber 30 and an outerchamber 32. A lower portion of the inner wall 28 defines an opening 34.An ash support member 36 is affixed to a lower portion of the inner wall28 by rigid members 38 so that the ash support member 36 is disposed adistance below the opening 34. The outer periphery of the ash supportmember 36 is relatively free from obstructions about the vast majorityof the outer periphery, providing relatively open side passagewaysbetween the inner wall 28 and the ash support member 36. This allows ashto spill from the ash support member 36 preferably over at leastapproximately 80 percent of the outer periphery of the ash supportmember 36, more preferably over at least approximately 90 percent of theouter periphery of the ash support member 36, and most preferably overat least approximately 95 percent of the outer periphery of the ashsupport member 36.

A gas injection ring 40 is affixed to the inner wall 28 and is disposedat a medial point of the inner chamber 30. Openings 42 in the inner wall28 provide a flow path for gas, such as air or an air and fuel mixture,to pass from a plenum 44 formed by the ring 40 into the inner chamber30. A conduit 46 extends through the outer wall 20 of the vessel 12 andis operably connected to the ring 40. The conduit 46 is connected to anair source and is preferably connected to a fuel source, such as asource of natural gas or propane. As seen in FIG. 1, a recycle line 48may also be provided to return a portion of the combustible gasgenerated by the system 10. An igniter 50, such as a spark plug igniter,is disposed in the conduit 46 adjacent to the reaction vessel 12.

A fuel agitator, such as a fuel stirring member 52 is provided in theinner chamber 30. The fuel stirring member 52 is preferably disposedabove the opening 34 and is more preferably disposed above the ring 40.Similarly, an ash agitator, such as an ash stirring member 54 isprovided inside the vessel 12, below the ring 40 and above the ashsupport member 36. Another ash agitator, such as ash stirring member 55is provided inside the vessel 12, below the ash support member 36.Coaxial shafts 56 and 58 extend upward from the stirring members 52, 54and 55 to or above an upper portion of the reaction vessel 12. Motors 60and 62 are operably connected to the shafts 56 and 58 for rotating theshafts and stirring members 52, 54, and 55.

The frustoconical, lower base portion 22 of the reaction vessel 12extends below the ash support member 36. An opening is provided at thebottom of the lower base portion 22 to allow ash to pass from thereaction vessel 12 to an ash removal system 64, such as an auger drivefor solids transfer. A conduit 66 is provided through the outer wall ofthe vessel 12 in an upper portion of the outer chamber 32 to provide apath for combustible gases generated within the reaction vessel 12 topass from the reaction vessel 12.

A fuel level sensor 68 is provided in the inner chamber 30, preferablyabove the opening 34, more preferably above the ring 40, and mostpreferably above the fuel agitator 52. The fuel level sensor 68 isoperably coupled with the feed line 24 to automate the process ofmaintaining fuel at a desired level within the inner chamber 30. An ashlevel sensor 70 is disposed within the reaction vessel 12, preferablybelow the opening 34, more preferably below the ash agitator 54, andmost preferably below the ash support member 36. The ash level sensor 70is operably coupled with the ash removal system 64 to automate theprocess of maintaining ash at a desired level within the reaction vessel12. It is of course understood that the reaction vessel 12 may take anynumber of sizes, shapes, and configurations. It is also understood thatthe vessel 12 need not be open at the top and need not be a downdraftreaction vessel 12.

Conduit 66 connects the reaction vessel 12 with the scrubber housing 14,providing a flow path into a lower portion of the scrubber housing 14. Apump 72 is provided to pass a liquid such as water through a water feedline 74 into an upper portion of the scrubber housing 14 and throughsprayers. A water return line 76 is connected to a lower portion of thescrubber housing 14 for returning water to the pump 72 for reuse withinthe scrubber housing 14. A feed line 78 may also be provided forproviding a source of fresh water. Wash lines 80 may be provided forintermittent use as described below. Scrubbed gas exits through conduit82 that is disposed at an upper portion of the scrubber housing 14. Askim line 84 is provided at a lower portion of the scrubber housing 14,and a blow down line 86 is provided at the bottom of the scrubberhousing 14. A level sensor 88, such as a float switch is disposed in thescrubber housing 14 for maintaining liquid levels within the scrubberhousing 14 at desired levels. It is of course understood that thescrubber housing 14 may take any number of shapes, sizes, andconfigurations.

Conduit 82 passes from the scrubber housing 14 to blowers 90. As bestseen in FIG. 3, the blowers 90 are heavy duty hybrids that combinedesirable features of blowers designed for moving gases and pumpsdesigned for moving liquids. Walls forming the impeller housing 92preferably have a wall thickness of approximately ¾ inch. A sealingmember 94, such as an O-ring is used to create an airtight andwatertight seal between the walls forming the impeller housing 92.Referring to FIG. 4, the impeller blades 96 are curved and are thickerthan impeller blades of common blowers designed for moving gases,preferably approximately 50 percent thicker. A packing gland 98, similarto a packing gland used in a water pump is used to provide a shaft 100seal. Additional sets of bearings 102 are also used in connection withthe impeller shaft 100. It is preferred to use at least three sets ofbearings 102 and it is more preferred to use at least four sets ofbearings 102. Conduit 104 passes from the blowers 90 to the filterhousing 16, providing a flow path into a lower portion of the filterhousing 16. It is of course understood that the blowers 90 may bedisposed at any number of locations in the system 10 and that theblowers 90 may take any number of different sizes, shapes, andconfigurations. It is also understood that, although not preferred,conventional blowers may be used.

The filter housing 16 is preferably packed with wood chips. Conduit 106passes from an upper portion of the filter housing 16 to provide a flowpath for the scrubbed and filtered combustible gas. Additional conduits108, 48, and 110 are also provided for passing the scrubbed, filteredcombustible gas to flare, to recycle, and for further uses. A conduit112 passes from a lower portion of the filter housing 16 for removingwastewater and other matter that condenses or is removed from the gas asit passes through the filter housing 16. It is understood that thefilter housing 16 may take any number of shapes, sizes, andconfigurations and that any number of different filter media orcombinations of filter media may be used.

Conduits 84, 86, 112, and 114 connect the scrubber housing 14 and filterhousing 16 to a recycle housing 18, providing a flow path into an upperportion of the recycle housing 18. Return line or conduit 116 passesfrom a lower portion of the recycle housing 18 to pump 118 and line 26passes from pump 118 to reaction vessel 12. A recirculation line 120 isprovided for diverting a portion of the liquid from the return line 26back to the recycle tank 18. A level sensor 122, such as a float switch,is disposed in the recycle housing 18 for maintaining liquid levelswithin the recycle housing 18 at desired levels. It is understood thatthe recycle housing 18 may take any number of different shapes, sizes,and configurations.

In operation, feed line 24 provides a solid carbonaceous fuel to thereaction vessel 12. The solid fuel drops through the inner chamber 30,accumulates on the ash support member 36, and builds up within the innerchamber 30 to a level above the ring 40 and then above the fuel stirringmember 52. An oxygen source, such as air, is provided via conduit 124 ,and an alternate fuel source is provided via conduit 126. The air andalternate fuel are mixed, ignited by igniter 50, and pass through thering 40 and into the inner chamber 30. The burning air and alternatefuel mixture ignites the carbonaceous fuel within the inner chamber 30.As the carbonaceous fuel sources pass downward within the inner chamber30, the carbonaceous fuel sources are at least partially combusted toproduce, among other things, ash and a combustible gas. Fuel stirringmember 52 keeps the different fuel sources blended and reduces orprevents channeling and similar problems.

Ash passes through opening 34 and collects on ash support member 36. Theash stirring member 54 prevents ash build up by moving the collectingash outward so that the ash spills or passes from the outer periphery ofthe ash support member 36 down to the lower base portion 22 of thereaction vessel 12. Other than the ash stirring member 54 and supportmembers 38, the area between the opening 34 of the inner wall 28 and theash support member 36 is substantially unobstructed to provide a readypath for ash removal free from obstructions and sources of clogging suchas grates or mesh materials. In that regard, the support members 38connect the ash support member 36 to the inner wall 28 in a manner thatallows ash to spill from the ash support member 36 preferably over atleast approximately 70 percent of the outer periphery of the ash supportmember 36, more preferably over at least approximately 80 percent of theouter periphery of the ash support member 36, and most preferably overat least approximately 90 percent of the outer periphery of the ashsupport member 36.

Ash that accumulates in the lower base portion 22 of the reaction vessel12 passes through an opening in the bottom of the reaction vessel 12 andis removed by an ash removal system 64, such as by an auger or screwdrive. The auger drive 64 is operably coupled with ash level sensor 70to maintain the ash in the reaction vessel 12 below a desired amount.The ash removed from the reaction vessel 12 will typically be a salableproduct.

The fuel level sensor 68 is operably coupled with the solid fuel feedline 24 to maintain solid fuel within a desired height range within theinner chamber 30. The desired height range will vary depending upon anumber of factors, including but not limited to the properties of thesolid fuel. It is typically desirable to maintain the solid fuel levelwithin the inner chamber 30 at the lowest possible level while stillmaintaining an adequate seal to prevent products of combustion fromescaping through the top of the reaction vessel 12. The level desiredwill vary with factors such as the density and moisture content of thesolid fuel. For example, the desired level for a solid fuel comprisedprimarily of chicken litter will be higher than the desired level for asolid fuel comprised primarily of wood pulp or paper mill sludge, andthe desired level for a solid fuel comprised primarily of wood pulpsludge will be higher than the desired level for a solid fuel comprisedprimarily of sanding dust. In a typical operation in which the solidfuel is comprised primarily of chicken litter, the level of solid fuelwithin the inner chamber 30 is preferably maintained at a height ofapproximately 8 inches to approximately 10 inches above the ring 40.Similarly, in an operation in which the solid fuel is comprisedprimarily of wood pulp sludge, the level of solid fuel within the innerchamber 30 is preferably maintained at a height that is only slightabove the ring 40. Also, in an operation in which the solid fuel iscomprised primarily of sanding dust, the level of solid fuel within theinner chamber 30 is preferably maintained at a height that isapproximately even with or slightly below the ring 40.

The blowers 90 draw gaseous products of combustion downward through thereaction vessel 12 so that they pass through the opening 34 in the innerwall 28 and upwardly through the outer chamber 32 before passing throughconduit 66. Combustible gas from the reaction vessel 12 enters a lowerportion of the scrubber housing 14 and passes upward toward conduit 82.Pump 72 circulates water to the scrubber housing 14. Water enters thescrubber housing 14 through conduit 74, passes through sprayers, andcontacts the combustible gas. The water cools and scrubs the combustiblegas, removing matter from the combustible gas including tar, oil, andparticulate matter. The water level in the scrubber housing 14 ismaintained at a desired level so that tar, oil, and similar matter maybe removed from the scrubber housing 14 via the skimmer line 84.Particulate matter and other components that settle to the bottom of thescrubber housing 14 are periodically removed via blow down line 86.Valves 128 are also opened periodically so that the pump 72 maycirculate water through wash lines 80 and through conduits 66, 82, and104 for cleaning. From time to time, valve 130 may be opened so that thewater in scrubber housing 14 may also be drained through line 86 andreplaced with fresh water from line 78.

The scrubbed combustible gas exits the scrubber housing 14 through line82, passes through blowers 90 and is driven through filter housing 16.As it exits the scrubber housing 14, the gas may also be passed througha filter/knock-out pot, before being passed to the blowers 90. Woodchips in the filter housing 16 dry the gas and remove additional amountsof particulate matter and other pollutants. Wastewater and other matterthat are removed from the combustible gas and that are not absorbed bythe wood chips fall to the bottom of the filter housing 16 and areremoved via line 112. Scrubbed, filtered combustible gas exits thefilter housing 16 via line 106. From there the combustible gas isflared, returned to the reaction chamber, or sent to other uses. Duringinitial start-up phase, the combustible gas is flared until it isdetermined that gas is being produced at a desired quantity and quality.Once the start-up phase is complete, the combustible gas will primarilybe passed via line 110 to produce work elsewhere. For example, thecombustible gas might be combusted to supply heat to a process or mightbe combusted within a motor or turbine to produce work or to generateelectricity. As additional examples, the combustible gas produced by thesystem 10 may be used in brooder heaters in poultry houses, in internalcombustion engines, and in boilers. In fact, the combustible gasgenerated by the present system 10 compares quite favorably with naturalgas, often being cleaner while having comparable or higher heatingvalues. The heating values of the combustible gas produced will varydepending upon a number of factors, such as the type, composition, andmoisture content of the carbonaceous fuel provided, but the heatingvalues of the combustible gas produced will typically be at or near 550BTU per cubic foot. Accordingly, combustible gas produced using thepresent system 10 is a good candidate for use in any situation thatcurrently uses natural gas or propane.

Depending upon the properties of the carbonaceous fuels being suppliedto the reaction vessel 12, such as the moisture content, a portion ofthe combustible gas may be returned to the reaction vessel 12 via line48 to supply additional fuel to aid in the partial combustion of thecarbonaceous fuel. The combustible gas supplied via line 28 may serve asa complete or partial replacement for the alternate fuel source suppliedto the reaction vessel 12 via line 126. Returning the combustible gas tothe reaction chamber 12 offers a number of advantages. For example, itsaves on fuel costs that might otherwise be required to maintain thedesired combustion in the reaction vessel 12. The combustible gas willtypically burn at higher temperatures than natural gas, and the highertemperatures are often desirable in the reaction vessel 12. For example,natural gas may burn at a temperature of approximately 1400° F., whereasa typical combustible gas produced using the present system 10 may burnat a temperature of approximately 2200° F.

Lines 86, 84, 112, and 114 pass from the scrubber housing 14 and thefilter housing 16 to recycle housing 18. These lines 86, 84, 112, and114 pass wastewater, excess water from wet fuel components, tar, oil,particulate matter, and other removed substances to an upper portion ofthe recycle housing 18. These components pass from the recycle housing18 via line 116, and pump 118 passes these components via line 26 backto the reaction chamber 12, where they are fed into an upper portion ofthe reaction vessel 12. A portion of these components is diverted vialine 120 and returned to the recycle tank 18 to help stir or agitate thecontents of the recycle tank 18. Returning the wastewater and othercomponents to the reaction vessel 12 provides a number of advantages.For example, the wastewater scavenges additional, residual carbon fromthe ash as the water is broken down. This provides for better recoveryof the heating value from the carbonaceous fuel and eliminates ordrastically reduces the need to dispose of wastewater.

The system 10 may be used to process a wide variety of carbonaceousfuels, as well as combinations thereof. The spacing between the ashsupport member 36 and the opening 34 of the inner wall 28, as well asthe relatively unobstructed side openings there, allow a wide assortmentof solid fuels to be used without fear of clogging. Possiblecarbonaceous fuels include but are not limited to things such as chickenlitter, other animal waste, municipal solid waste, glued woods (such asplywood and press board), paper mill or wood pulp sludge (includingsludge with a moisture content of 65% or higher), wood or yard waste,and shredded tires. Liquid carbonaceous fuels may also be added,including but not limited to waste motor oil and cooking oil. Addingthese liquid carbonaceous fuels can markedly increase the heating valueof the combustible gas produced.

The following emissions test examples illustrate that the gasificationsystem 10 of the present invention can produce combustible gas that isenvironmentally friendly while dispensing with solid carbonaceous fuelsthat previously posed serious landfill issues.

EXAMPLE 1

An emissions test was conducted on combustible gas generated by thesystem 10 while combusting chicken litter. A sample run of 60 minutes induration was performed. Testing was performed in accordance with themethods detailed in 40 C.F.R., Part 60, Appendix A. The flow, based onthe lowest recordable flow, had a velocity of 6.77 feet per second, andthe sample collected had a volume of 41.42 dry standard cubic feet. Theresults of the emissions testing are summarized in Table 1 below. TABLE1 Emissions Substance (lbs/hr) Particulate Matter (based on lowestdetectable flow rate) 0.003 VOC as Propane (corrected for moisture)0.137 Nitrogen Oxides as NO₂ 0.001 Carbon Monoxide 0.003 Sulfur Dioxide0.096 Ammonia 0.033 HCl 0.008 Chloride 0.005

EXAMPLE 2

An emissions test was conducted on combustible gas generated by thesystem 10 while combusting paper mill sludge. A sample run of 60 minutesin duration was performed. Testing was performed in accordance with themethods detailed in 40 C.F.R., Part 60, Appendix A. The flow, based onthe lowest recordable flow, had a velocity of 6.53 feet per second, andthe sample collected had a volume of 40.60 dry standard cubic feet. Theresults of the emissions testing are summarized in Table 2 below. TABLE2 Emissions Substance (lbs/hr) Particulate Matter (based on lowestdetectable flow rate) 0.0014 VOC as Propane (corrected for moisture)0.014 Nitrogen Oxides as NO₂ 0.013 Carbon Monoxide 0.051 Sulfur Dioxide0.017

Other modifications, changes and substitutions are intended in theforegoing, and in some instances, some features of the invention will beemployed without a corresponding use of other features. For example, theconfiguration of the ash support member 36 may be used in combinationwith any number of different gasification systems, regardless of whethersuch systems also use other features of the present invention, and mayalso find uses in systems other than gasification systems. Similarly,the wastewater return features of the present invention may be used incombination with any number of different gasification systems,regardless of whether such systems also use other features of thepresent invention, and may also find uses in systems other thangasification systems. Further, the wood chip filtering of the presentinvention may be used in combination with any number of differentgasification systems, regardless of whether such systems also use otherfeatures of the present invention, and may also find uses in systemsother than gasification systems. Further still, the hybrid blower 90design of the present invention may be used in combination with anynumber of different gasification systems, regardless of whether suchsystems also use other features of the present invention, and may alsofind uses in systems other than gasification systems. Of course,quantitative information is included by way of example only and is notintended as a limitation as to the scope of the invention. Accordingly,it is appropriate that the invention be construed broadly and in amanner consistent with the scope of the invention disclosed.

1. A method, comprising: (1) at least partially combusting acarbonaceous fuel to produce a combustible gas; (2) passing saidcombustible gas through sprayed water to produce a scrubbed gas; (3)passing said scrubbed gas through wood chips; and (4) after step (3),combusting said scrubbed gas.
 2. The method of claim 1, wherein step (1)comprises: at least partially combusting said carbonaceous fuel toproduce said combustible gas, said carbonaceous fuel comprising chickenlitter.
 3. The method of claim 1, wherein step (1) comprises: at leastpartially combusting said carbonaceous fuel to produce said combustiblegas, said carbonaceous fuel comprising wood pulp sludge.
 4. The methodof claim 1, wherein: step (1) comprises at least partially combustingsaid carbonaceous fuel in a reaction vessel to produce said combustiblegas; and step (2) comprises passing said combustible gas through saidsprayed water in a scrubber housing to produce said scrubbed gas; andfurther comprising passing wastewater from said scrubber housing to saidreaction vessel.
 5. The method of claim 1, wherein: step (1) comprisesat least partially combusting said carbonaceous fuel in a reactionvessel to produce said combustible gas; and step (3) comprises passingsaid scrubbed gas through said wood chips in a filter housing; andfurther comprising passing wastewater from said filter housing to saidreaction vessel.
 6. The method of claim 4, wherein: step (3) comprisespassing said scrubbed gas through said wood chips in a filter housing;and further comprising: passing wastewater from said filter housing tosaid reaction vessel.
 7. The method of claim 1, wherein: step (1)comprises at least partially combusting said carbonaceous fuel in areaction vessel to produce said combustible gas; step (2) comprisespassing said combustible gas through said sprayed water in a scrubberhousing to produce said scrubbed gas; and step (3) comprises passingsaid scrubbed gas through said wood chips in a filter housing; andfurther comprising: passing wastewater from said scrubber housing to arecycle tank; passing wastewater from said filter housing to saidrecycle tank; and passing said wastewater from said scrubber housing andsaid wastewater from said filter housing from said recycle tank to saidreaction vessel.
 8. A method, comprising: (1) at least partiallycombusting a carbonaceous fuel in a reactor vessel to produce acombustible gas; (2) passing said combustible gas to a scrubber housing;(3) spraying a liquid on said combustible gas within said scrubberhousing; and (4) passing a first portion of said liquid from saidscrubber housing to said reactor vessel.
 9. The method of claim 8,wherein step (3) comprises: spraying said liquid on said combustible gaswithin said scrubber housing, said liquid comprising water.
 10. Themethod of claim 8, wherein step (3) comprises: spraying said liquid onsaid combustible gas within said scrubber housing to remove matter fromsaid combustible gas, said matter comprising tar and oil; and furthercomprising: passing said tar and oil from said scrubber housing to saidreactor vessel.
 11. The method of claim 8, further comprising: passingsaid combustible gas from said scrubber housing to a filter housing; andpassing a waste liquid from said filter housing to said reaction vessel.12. The method of claim 8, wherein step (4) comprises: passing saidfirst portion of said liquid from said scrubber housing to a recyclehousing; and passing said first portion of said liquid from said recyclehousing to said reaction vessel.
 13. The method of claim 12, whereinstep (3) comprises: spraying said liquid on said combustible gas withinsaid scrubber housing to remove matter from said combustible gas, saidmatter comprising tar and oil; and further comprising: passing said tarand oil from said scrubber housing to said recycle housing; and passingsaid tar and oil from said recycle housing to said reactor vessel. 14.The method of claim 13, further comprising: passing said combustible gasfrom said scrubber housing to a filter housing; passing waste liquidfrom said filter housing to said recycle housing; and passing said wasteliquid from said recycle housing to said reaction vessel.
 15. Acombination, comprising: a reaction vessel having an upper outer wallportion and a lower base portion; an inner wall disposed within saidvessel, an upper portion of said inner wall being connected to saidvessel to form an inner chamber and an outer chamber, a lower portion ofsaid inner wall defining a first opening within said vessel; an ashsupport member disposed within said vessel below said first opening,said ash support member being affixed within said vessel so that ash mayspill from said ash support member over at least approximately 80percent of an outer periphery of said ash support member.
 16. Thecombination of claim 15, wherein said ash support member is affixedwithin said vessel so that ash may spill from said ash support memberover at least approximately 90 percent of said outer periphery of saidash support member.
 17. The combination of claim 15, further comprising:a first agitating member disposed within said reaction vessel above saidopening; and a second agitating member disposed within said reactionvessel below said opening.
 18. The combination of claim 15, furthercomprising: a scrubber housing, said scrubber housing being operablyconnected to said reaction vessel to provide a flow path from said outerchamber of said reaction vessel to said scrubber housing; a filterhousing, said filter housing being operably connected to said scrubberhousing; and wood chips disposed in said filter housing.
 19. Thecombination of claim 15, further comprising: a blower disposeddownstream from said reaction vessel and operably connected to saidreaction vessel for withdrawing a combustible gas from said reactionvessel, said blower comprising: an impeller housing; an impellerdisposed within said impeller housing; and an O-ring, said O-ringdisposed to provide a seal between portions of said impeller housing.20. The combination of claim 19, said blower further comprises: a shaftaffixed to said impeller; and at least three sets of bearings operablyconnected to said shaft.